This is a supplement application to DA 00942. DA 00942 is a project which is in progress and is entitiled "Stereoselective Pharmacology and Pharmacokinetics of Methadone." A considerable amount of new data has been discovered and reported in the first year of this project. The half life of each isomer of methadone and the racemic mixture is being examined in mice, rats, the isolated perfused rat liver and in isolated microsomal preparations. New metabolites of methadone have been identified by gas chromatography and mass spectrometry, including of dihydroxylated glucuronide. A new specific radioimmunoassay of methadone has been developed and is comparable to a new and highly specific multiple ion detection assay, which has also been developed in our laboratory. This is a supplement to our current grant and is entirely for the purchase of a new, modest liquid scintillation counter. We urgently require additional counting facilities for C14 and tritium. There is only one old fashioned machine in the Department of Pharmacology and six different faculty members are using this instrument, which is over ten years old and has inferior photomultiplier tubes, resulting in a very low efficiency for the counting of carbon 14 and tritium. Consequently it is necessary for us to use up-to-date counters in other departments (pediatrics, biochemistry, physiology) and even with this alternative arrangement delays and inefficiency are hampering the rapid progress of our work. It is for this reason that we have applied for additional funds to purchase a 100 sample new liquid scintillation counter (Beckman LS 150).